Author

Abstract

Transmission electron microscopy (TEM) has been used to study the interfacial microstructure formed by reacting Al-Mg alloy with mullite (Al6Si2O13) at high temperature (>900 ⁰C). The TEM study was used in order to understand the strong effect of Mg addition on the nature of the reaction between Al and mullite used to form Al/Al2O3 composite. After reaction at 1050 ⁰C, the formation of a layered structure between the Al-1% Mg alloy and mullite was observed. An alloy layer with a much higher concentration of Mg than the starting alloy was found present next to the initial mullite surface. Between the alloy layer and mullite, a dense and continuous layer made of small MgAl2O4 (spinel) and Si particles was present. The layer apparently stopped further reaction between Al-Mg alloy and mullite by preventing transport of the metals to the reaction front and the Si reaction product away from the reaction front. The microstructure resulting from the initial reaction indicated the reaction proceeded by replacing Si atoms with Al and Mg atoms on mullite&lcub;210&rcub; lattice planes and forming MgAl2O4&lcub;311&rcub; lattice planes simultaneously.